Session IX - Basic Science

Anabolic Supplementation in Fracture and Muscle Repair

Peter Kazmier, MD¹; Michael S. Hughes, BS¹; Jeffrey O. Anglen, MD²; Aaron A. Stoker, PhD¹; Keiichi Kuroki, DVM, PhD¹; Timothy A. Burd, MD¹; James L. Cook, DVM, PhD¹; (all authors-a-OTA/EBI-Biomet Grant)

¹University of Missouri-Columbia, Columbia, Missouri, USA;

²Indiana University, Indianapolis, Indiana, USA

Purpose: Previous studies have demonstrated that dietary supplementation using a high protein diet of essential amino acids caused malnourished rats with femoral fractures to increase body weight, muscle mass, bone mineral density and relative bone density at the fracture site, and torsional strength of fracture callus compared to isocaloric diets with lower protein levels. In this study, the messenger RNA (mRNA) levels for various growth factors and muscle proteins were examined from those animals to begin to elucidate the mechanism.

Methods: 100 adult rats were studied; 10 animals served as controls, receiving a 15% protein diet throughout the study. After a 5-week malnourishment phase, 3 treatment groups were formed (30 per group): Group P6 (malnourished diet) received 6% protein, Group P15 (regular diet) received 15% protein, and Group P30 (anabolic diet) received 30% anabolic protein diets. At 2 weeks after creation of a fracture, the quadriceps and femurs were harvested bilaterally. Total protein content (g/gm of muscle) was determined for a section of quadriceps from each muscle specimen using SDS-PAGE (gel electrophoresis). IGF-1 and IGF-2 along with their corresponding receptors, actin, myosin (subtypes 1b,2a,2b,2d), and VEGF mRNA were quantified.

Results: The mRNA expression for IGF-1 and IGF-2, IGF receptors, myosin, and VEGF were all significantly decreased in the P30 group when compared to all other groups and in the P15 group compared to the P6 group (all values P<0.045). The total protein content of muscle in the fractured limb was 23% greater in the P30 group compared to the P15 and P6 groups (P<0.05). The total protein content of muscle from the nonfractured limb was 13% and 15% greater in the P30 group compared to the P15 and P6 diet groups, respectively (P<0.05).

Conclusion: There were striking differences in the amount of growth factor mRNA transcribed. There was a significant stepwise elevation in mRNA for IGF-1 and IGF-2 and the corresponding receptors as dietary levels decreased. The amount of VEGF mRNA in the P6 group was increased by a factor of over 300 compared to the P30 group. These results indicate that soft tissues with the higher mRNA expression were unable to effective translate the mRNA into functional proteins, thus disturbing the tissues' ability to heal at all time intervals.

Significance: By examining the effects of various nutritional supplementation regimens on muscle recovery, fracture healing, and overall health in orthopaedic trauma, we may be able to isolate anabolic elements that lessen complications, morbidity, and possibly mortality.